The present invention relates generally to portable communication devices and more particularly to portable radio devices that require audio operation capability over extreme temperatures. Portable battery-powered communication devices are advantageous in many environments, but particularly in public safety environments such as fire rescue, first responder, and mission critical environments. Portable communication devices used by public safety personnel include, for example, portable radios operated in conjunction with accessories, such as remote speaker microphones and other audio accessories that must operate over extreme temperature conditions. The ability to have a product rated as compliant with certain test specifications, for example temperature compliance specifications outlined in the National Fire Protection Association Specifications (NFPA1802) can be very beneficial in achieving high product satisfaction.
Challenges arise when designing public safety radios and their associated audio accessories where the audio includes a digital processing unit where most components used for digital processing are not capable of operating to required temperature extremes. While some known techniques have been acceptable for normal radio operation, such techniques are not deemed acceptable for mission critical operation. For example, simply turning off certain audio functions under high temperatures is not considered acceptable under mission critical operation. Likewise reducing performance of mission critical audio, such as by reducing audio gain is not considered acceptable.
Accordingly, there is a need for a portable radio with improved audio operation capability over expanded temperature range for mission critical operation.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.